Scott,
With the thread drift here yesterday, I DO hope you're still reading, since I have a good deal of important info for you.....

Quote:

Originally Posted by MentalDungHeap

Hi, First post,
I'm looking at getting a 12v watermaker and want to know if they work while underway.

1) The answer is, of course, YES....
And, most never need any special tanks, etc......

I'm more of a voyager than a cruiser (I'm at sea a lot), and as such I make water underway all the time.....no matter what the sea state, I've never had any problems at all....~ 3 years, 10,000+ miles, multiple Atlantic crossings, etc. and no problems making water, underway or at anchor....

And, for a very helpful and well written article about watermaker choice and installation on a Pearson 424, please have a look here...Whoosh - Watermaker
{You'll probably find Jack's writing to be a bit more logical (less scattered) than mine.....and of course, since he's writing about his installation on the same model boat that you have, a Pearson 424, this should be of great help to you....}

Quote:

The big issue for me is that I plan to use a prop shaft alternator to get more power while sailing and would like to use some of those amps to make water if feasable.

2) And, as for a prop-shaft alternator......they do work in some cases, but are VERY boat specific and the "towed-water-generators" have many advantages......
I've written about my Hamilton Ferris Towed-Gen in a article.....and on the SSCA Discussion Boards as well.....
And, here again, Jack has written a very nice article about his choices, for a towed-water-generator, for his 424......

Have a look at his article here...Tow Generator
(Jack also includes some links to some SSCA discussions on this topic....)

3) And, don't forget to do a search on the SSCA discussion boards ("Energy" and "Boat Systems and Maintenance") for prop-shaft alt / towed-water-gen, and for watermakers......and you'll read a lot of real world info, for those out there using them.....SSCA Discussion Board &bull; Index page

Again Scott, I do hope you get a chance to read thru all of the above links, since many of your questions will be answered, as well as Jack's articles being directly on point to YOUR application on you Pearson 424....

Well thanks for all the info, and I am still reading John.
Your post was great and I have already read a few of the threads that you mentioned.
I was looking at the 80E, one was on ebay but I let it get away. So all the posts are of help and I'm still at the shoping stage of the wm.

I'm still prioritizing the new additions to the boat and asked about the WM because fo the good deal. When it got up above $2100 I decided to keep looking.

I guess Tellie either works for or is Spectra from things he mentioned. I got the same smart-A attitude when I contacted Spectra several years ago.

I appreciate being corrected when I'm wrong, and I was wrong about the Amp Hours per Gallon these days. However I also got a lot of feedback about the low reliabilty of Spectra pumps, so maybe the 40% more power is worth it.

I do not appreciate being told I'm all wrong about a method that has worked flawlessly for years. I did preface the post about that method with "This is what works for me." There are a lot of right ways to do things, and a lot more wrong ways. My motive was to describe one of the right ways.

[QUOTE=rickmorel;390533]I guess Tellie either works for or is Spectra from things he mentioned. I got the same smart-A attitude when I contacted Spectra several years ago.

I appreciate being corrected when I'm wrong, and I was wrong about the Amp Hours per Gallon these days. However I also got a lot of feedback about the low reliabilty of Spectra pumps, so maybe the 40% more power is worth it.

I do not appreciate being told I'm all wrong about a method that has worked flawlessly for years. I did preface the post about that method with "This is what works for me." There are a lot of right ways to do things, and a lot more wrong ways. My motive was to describe one of the right ways.

Rick[/QUOTE.

Sorry you took my response as smart ass. I was hoping my comments like
"Rick, welcome aboard always good to have new people posting." and " Hey Rick, disagree away, it's more fun that way." and " I bet we'd have fun talkin watermakers over a few beers." was a bit self explanatory as to my good intenions. I make as best an effort to treat everybody with as much respect as I can. If you took my corrections in the wrong way I apologize. It was not my intent to insult. If we ever meet, the offer for a few beers still stands anyway, with the first few rounds on me.
Best Regards,
Tellie

Back to the original question, there are three reasons you'll want to make water underway. First, the noise is less bothersome while sailing than while at anchor. Second, you'll generally get cleaner water when out of the harbor, which means less filter clogging. Third, it means less rationing of water during long passages. In other words, you'll be able to shower mid-ocean.

Sorry you took my response as smart ass. I was hoping my comments like
"Rick, welcome aboard always good to have new people posting." and " Hey Rick, disagree away, it's more fun that way." and " I bet we'd have fun talkin watermakers over a few beers." was a bit self explanatory as to my good intenions. I make as best an effort to treat everybody with as much respect as I can. If you took my corrections in the wrong way I apologize. It was not my intent to insult. If we ever meet, the offer for a few beers still stands anyway, with the first few rounds on me.
Best Regards,
Tellie

Tellie, most of your response was "make nice", but there really were a few of the smart A in there. That's one of my few "buttons".

Okay, let's kiss and make up, then later when our paths cross someplace we can fight over who'll buy the first few rounds

I do respect the opinions of others and can always agree to disagree. It is fun to good naturedly debate various things. It's amazing how that can lead to new ideas and "slap oneself on the forehead" realizations.

I have a system that is largely based on the Spectra 380c. Let me say up front, I am very biased toward this system. This is based on its reliability and efficiency on my boat. The only issue I have had was the need to replace a defective motor when I originally purchased the used pieces.

I did not consider the cavitation issue when I installed my water maker and consequently did not consider this issue. I used the through-hull that was previously used by my water cooled refrigeration system. This is placed very near the center line of boat on the port hull. It is at the bottom of that hull, probably about 2 feet below the waterline. I almost always run the water maker while underway. I find I typically have excess power being generated during that period, so I take the opportunity to completely top off all tanks.

I have not been aware of any issues while using this regime. I have not used the system lately. I discarded the old membrane, that I had used for about 2 1/2 years. I have two pre-filters (20 and 5 microns) that I replaced regularly.

I have a system that is largely based on the Spectra 380c. Let me say up front, I am very biased toward this system. This is based on its reliability and efficiency on my boat. The only issue I have had was the need to replace a defective motor when I originally purchased the used pieces.

I did not consider the cavitation issue when I installed my water maker and consequently did not consider this issue. I used the through-hull that was previously used by my water cooled refrigeration system. This is placed very near the center line of boat on the port hull. It is at the bottom of that hull, probably about 2 feet below the waterline. I almost always run the water maker while underway. I find I typically have excess power being generated during that period, so I take the opportunity to completely top off all tanks.

I have not been aware of any issues while using this regime. I have not used the system lately. I discarded the old membrane, that I had used for about 2 1/2 years. I have two pre-filters (20 and 5 microns) that I replaced regularly.

The 380C uses two shurflo pumps as you know. They are far more forgiving of air ingress. They can run dry for a long time without damage (not recommnded of course) Larger systems with vane and plunger type pumps won't tolerate running dry for long. Some can be ruined quite quickly. These type pumps can be more sensitive to air but a little air rarely affects even those. Most small amounts of air that work it's way into watermakers underway is usually areated into fine small bubbles capable of passing through without any effect.

I agree with ka4wja that an sea chest or tank may not be needed it depends on the boat, boat speed through the water, and hull shape. ka4wja sailing a mono where the inlet may be lower in the water and less suseptable to aeration.

In my case, Makai is a cat which a max raw water inlet depth of 2 and half feet. The shallower draft and and differences in hull shape creates lots of areation. Before installing the tank the max speed was about 3 knots without areation and relativily flat seas. At higher speeds the bubbles begin. Since we rarely sailed below 5 -6 knots making water underway was a problem.

The sea chest solved our problem, but may not be required for your setup. The best way is setup assuming you will not need one but configure in such a way that it would be possible to retro fit a sea chest if needed.

__________________
Captain Bil formerly of sv Makai -- KI4TMM
The hunt for the next boat begins.http://www.sv-makai.com

Yeah, I think it can, but in that case, it's being used as an R/O water purifier. If I'm reading the Wikipedia article correctly, the process should not be as effective with less solute in the liquid (i.e., slower flow). You could also just contact the manufacturer and check it with them.

I've been told the problem in fresh water, without reducing pressure, is overheating the membrane from the increased flow.

I used a PUR 40E, 1.5 GPH, a lot in freshwater with no problems before I heard this. I assume the smaller ones don't have the overheat problems. We now have a PUR 80E, 3.4 GPH. I asked via their web page, but never got an answer. Next time we're in fresh I plan on trying it. I have to assume if the membrane housing gets warm what I've heard is true, but I really don't expect it to happen. I think the problem is with the much larger units. There is no way to adjust the pressure. Well, I guess it's the thing marked "DO NOT TURN".

I did notice with the 40E and a friend's 35E that output didn't change in fresh water.